In the adhesion between a metal and nitrile rubber (NBR), adhesives of chlorinated rubber series or novolak-type phenol resin series are used. The adhesive of chlorinated rubber series is not adhesible with a metal, so that a primer of phenol series must be applied thereto beforehand. Furthermore, owing to the high viscosity its applicability is also poor. To obtain better adhesion the primer film must have a thickness of at least 5 μm, causing troubles in case of parts requiring dimensional precision, fitting parts, or the like. On the other hand, the adhesive of novolak-type phenol series is adhesible only to (hydrogenated) NBR with a nitrile content of 30 to 40%, so that the applicable rubber range is limited, and also the adhesive contains hexamethylenediamine as a curing agent, causing troubles of gas generation during the drying and baking to foul the drier inside. Furthermore, all of these adhesives have a low resistance to various cryogenic liquids such as flon gases, water, PAG (polyalkylene glycol), etc., resulting in difficulty in application to cryogenic liquid sealing.
To solve these problems, the present applicant previously proposed a vulcanizable adhesive composition comprising a resol-type phenol resin, unvulcanized NBR, chlorinated polyethylene, etc. as essential components (JP-A-6-306340 and JP-A-8-302323). However, the proposed vulcanizable adhesive composition can give a good adhesion to (hydrogenated) NBR with a nitrile content of less than 30%, but still fails to show a good adhesion to (hydrogenated) NBR with a nitrile content of 40% or more, and has a better resistance to various cryogenic liquids than that of the afore-mentioned adhesives of chlorinated rubber series or phenol resin series, but still fails to meet the level of current requirement.